Well the first thing the UP did was take away several of the exercising power of the Corps because they saw little use in them so they really aren't.
Really being beholden to an organization that is ostensibly comprised of politicians and leaders of various disparate nations working in the name of their own interests is not the greatest prospects. Say what you will about the Guardians but they were committed to galactic peace and lived such a hermetic existence you could at least trust their integrity that they won't sell you out for a quick buck.